Molecular Biology - DNA Forms and Structures
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Questions and Answers

What characteristic distinguishes the Z form of DNA from the B form?

  • It forms triple-strand structures.
  • It is a left-handed helix. (correct)
  • It is a right-handed helix.
  • It contains 10 base pairs per turn.

    • Which of the following statements about denaturation of DNA is true?

  • It leads to hydrogen bond formation between strands.
  • It involves breaking the phosphate bonds.
  • It results in the formation of triple-stranded DNA.
  • It can be caused by increased temperature. (correct)

    • What type of DNA is formed when additional hydrogen bonds occur between the bases?

  • A form
  • Triple-strand DNA (correct)
  • B form
  • Bent DNA

    • How does bent DNA affect its structure?

    <p>It curves over a stretch of several bases.</p> Signup and view all the answers

    Which base pairing characteristic is associated with the A form of DNA?

    <p>Right-handed helical structure.</p> Signup and view all the answers

    What is the primary difference between RNA and DNA regarding their nitrogenous bases?

    <p>DNA contains thymine while RNA contains uracil.</p> Signup and view all the answers

    Which structure is formed when a base combines with a sugar?

    <p>Nucleoside</p> Signup and view all the answers

    What type of sugar is found in RNA?

    <p>D-ribose</p> Signup and view all the answers

    What is the structural difference between ribose and deoxyribose at the C2 position?

    <p>Deoxyribose has one less oxygen than ribose.</p> Signup and view all the answers

    What term is used for a nucleoside with one phosphate group added?

    <p>Mononucleotide</p> Signup and view all the answers

    Which nucleosides are associated with the bases adenine and guanine in RNA?

    <p>Adenosine and guanosine</p> Signup and view all the answers

    Which nitrogenous bases are considered purines?

    <p>Adenine and Guanine</p> Signup and view all the answers

    What characteristic distinguishes the tautomeric forms of purines and pyrimidines?

    <p>They undergo proton transfer affecting their functional groups.</p> Signup and view all the answers

    What characteristics define the double helical structure of DNA?

    <p>DNA is a right-handed double helix with two antiparallel strands.</p> Signup and view all the answers

    Which of the following nucleotide pairs are held together by two hydrogen bonds?

    <p>Adenine and Thymine</p> Signup and view all the answers

    Which of the following statements regarding nucleotides is correct?

    <p>DNA is composed of deoxyribonucleotides.</p> Signup and view all the answers

    According to Chargaff's rule, which pairing of bases has equal quantities in DNA?

    <p>Adenine and Thymine</p> Signup and view all the answers

    Which of the following best describes the composition of the DNA double helix's backbone?

    <p>It is hydrophilic due to its sugar and phosphate components.</p> Signup and view all the answers

    What feature is essential for maintaining the stability of the DNA double helix?

    <p>Hydrogen bonds between complementary base pairs</p> Signup and view all the answers

    What role do nucleotide analogs play in medical treatments?

    <p>They mimic nucleosides to combat viral infections.</p> Signup and view all the answers

    Which of the following describes the spacing of nucleotides in the DNA helix?

    <p>Each turn of the helix is 34 Å with 10 pairs of nucleotides.</p> Signup and view all the answers

    What is the primary role of nucleic acids in living organisms?

    <p>Transmission of genetic information</p> Signup and view all the answers

    Which type of nucleic acid serves as the genetic material in most organisms?

    <p>Deoxyribonucleic acid (DNA)</p> Signup and view all the answers

    What does the central dogma of molecular biology describe?

    <p>The flow of information from DNA to RNA to protein</p> Signup and view all the answers

    Which statement regarding RNA is correct?

    <p>RNA plays a role in protein synthesis in various forms.</p> Signup and view all the answers

    What key discovery was made by Oswald Avery and his colleagues?

    <p>Identified DNA as the material genes are made of.</p> Signup and view all the answers

    Which of the following sequences accurately represents the flow of genetic information?

    <p>DNA to RNA to protein</p> Signup and view all the answers

    What is the predominant structural form of DNA?

    <p>Double helix</p> Signup and view all the answers

    Which of the following scientists did NOT contribute to the discovery of the structure of DNA?

    <p>Henry Ford</p> Signup and view all the answers

    Which molecule serves as the building blocks of nucleic acids?

    <p>Nucleotides</p> Signup and view all the answers

    What role does messenger RNA (mRNA) have in cells?

    <p>It carries genetic information from DNA to ribosomes.</p> Signup and view all the answers

    In which year did Watson and Crick determine the structure of DNA?

    <p>1953</p> Signup and view all the answers

    What did the research by Sanger focus on?

    <p>Determining the sequence of bases in DNA</p> Signup and view all the answers

    What represents a difference between DNA and RNA?

    <p>DNA contains deoxyribose; RNA contains ribose.</p> Signup and view all the answers

    Study Notes

    Nucleic Acids

    • Nucleic acids store and transmit genetic information.
    • Two main types exist:
      • Deoxyribonucleic acid (DNA)
      • Ribonucleic acid (RNA)
    • DNA holds the instructions for making proteins.
    • RNA exists in various forms, aiding protein synthesis.

    Central Dogma of Life

    • Information flows from DNA to RNA to protein.
    • This flow describes most organisms' molecular biology, except some viruses which use RNA as their genetic repository.

    Brief History (of DNA research)

    • 1859: Charles Darwin published On the Origin of Species.
    • 1865: Gregor Mendel's research on heredity.
    • 1869: Friedrich Miescher discovered DNA.
    • 1902: Walter Sutton and Theodor Boveri proposed the chromosome theory.
    • 1910: Thomas Hunt Morgan, Calvin Bridges demonstrated genes are on chromosomes.
    • 1944: Oswald Avery, Colin McLeod, Maclyn McCarty identified DNA as the genetic material.
    • 1953: James Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins determined DNA's structure.
    • 1961: Sydney Brenner, Francois Jacob, Matthew Meselson discovered messenger RNA.
    • 1966: Marshall Nirenberg, Gobind Khorana finished unraveling the genetic code.
    • Subsequent events after 1966 include: the discovery of restriction enzymes, creation of first recombinant DNA in vitro, cloning of a sheep, determination of human genome sequence and others.

    Component of Nucleic Acid

    • Nucleic acids are polymers of nucleotides.
    • Nucleotides consist of a phosphate group, a sugar, and a nitrogenous base.
    • Nucleotides are held together by 3' and 5' phosphate bridges.

    Nucleotide

    • Nucleotides are the building blocks of nucleic acids.
    • They're composed of a nitrogenous base, a pentose sugar, and a phosphate group.
    • Nucleotides have various functions, including forming co-enzymes and participating in cellular energy reactions (e.g., ATP).
    • Nucleosides are base + sugar. A nucleotide is a nucleoside + phosphate.

    Nitrogenous Bases

    • Nitrogenous bases in nucleotides are aromatic, heterocyclic compounds.
    • Two types:
      • Purines (double ring)
      • Pyrimidines (single ring)
    • Purines: Adenine (A), Guanine (G)
    • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)

    Major Nitrogenous Bases (in DNA & RNA)

    • DNA and RNA share two purines (Adenine and Guanine).
    • However, DNA contains thymine (T), and RNA contains uracil (U) as the pyrimidine counterpart.

    Tautomeric Forms of Purines and Pyrimidines

    • Tautomerism in nucleic acid bases involves proton shifts within the heterocyclic ring.
    • Keto-enol and imino-amino tautomers are formed.
    • These forms are important for base-pairing in DNA and RNA.

    Other Biologically Important Bases

    • These bases include variations of the major purines and pyrimidines (ex. 1-methyladenosine, inosine).

    Sugars of Nucleic Acids

    • Pentose sugars (ribose and deoxyribose) are central to nucleic acid structure.
    • Ribose is in RNA, deoxyribose in DNA.
    • The two sugars differ structurally only by one oxygen atom at the 2' carbon position.

    Nomenclature of Nucleotides

    • Add a pentose sugar to the base to form a nucleoside.
    • Ribonucleosides form when the sugar is ribose.
    • Deoxyribonucleosides form when the sugar is deoxyribose.
    • Adding one or more phosphate groups to the nucleoside results in a nucleotide.
    • Prime notation (' ) distinguishes sugar carbon positions from base nitrogen positions.

    Nucleosides and Nucleotides

    • A table summarizing the names of important nucleosides and nucleotides (RNA and DNA variants)

    Nucleotide Analogs

    • Synthetic compounds similar to nucleosides/nucleotides used in treating viral infections (such as HIV and Hepatitis C).

    DNA - Polymer of deoxyribonucleotide

    • Composed of monomeric units:
      • Deoxyadenylate (dAMP)
      • Deoxyguanylate (dGMP)
      • Deoxycytidylate (dCMP)
      • Deoxythymidylate (dTMP)
    • Monomeric units joined by phosphodiester bridges.

    DNA Double Helix

    • Proposed by Watson and Crick in 1953.
    • The double helix is a twisted ladder structure.
    • Two strands are antiparallel.
    • Strands held together by hydrogen bonds between complementary bases (A-T and G-C).
    • The diameter of a DNA double helix is 20 Å.
    • Each turn of the helix is 34 Å, containing 10 base pairs.
    • A strand has hydrophobic bases inside, with hydrophilic phosphate backbone on the outside.
    • Other forms of DNA include triple-strand, bent DNA (with different shapes and functions.)

    Chargaff's Rule

    • Equal amounts of purines and pyrimidines in a DNA molecule.
    • The quantity of adenine equals the quantity of thymine, and the quantity of guanine equals the quantity of cytosine.

    Conformation of DNA Double Helix

    • DNA exists in many forms (e.g. B-form, A-form, Z-form).
    • A and Z forms represent non standard forms, unlike the common B-form.
    • These structural variations influence interaction and protein binding.

    Properties of Major Forms of DNA

    • Table summarizing the key properties of A-DNA, B-DNA, and Z-DNA forms.

    Other Types of DNA

    • Other conformations of DNA exist besides B-DNA, A-DNA, and Z-DNA
    • These variations are the result of different base sequences and interactions.

    Denaturation of DNA

    • Hydrogen bonds holding the two strands of DNA together are broken, leading to the separation of strands (into single strands).
    • Denaturation may result from pH change, temperature increase.
    • The phosphate-sugar backbone is not broken during denaturation.
    • The process can be quantifies by the increase in UV absorbance.

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    Related Documents

    Nucleic Acid_DNA Lecture Notes PDF

    Description

    Test your knowledge of the different forms of DNA, including the distinguishing features of Z and B forms. This quiz covers key concepts such as base pairing, denaturation, and the structural differences between RNA and DNA. Assess your understanding of nucleosides and sugars involved in DNA and RNA.

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